add_variables

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already indicate this is not read-only and not destructive; the description adds valuable atomicity behavior: on any item error the model is left unchanged and the error names the failing item (stage + index). This goes beyond the structured annotation hints.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences and front-loaded with the action and scope. The second sentence adds the critical all-or-nothing behavior without unnecessary detail.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's complexity and the rich input/output schemas, the description is sufficient: it states target, item types, batch nature, and error behavior. It does not need to explain return values because an output schema exists, though it could have explicitly mentioned using single-item tools for one-off additions.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has 100% description coverage for all 9 parameters, including per-item arrays and their nested fields. The tool description does not add extra parameter semantics beyond enumerating item types, so the baseline of 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool adds multiple stocks, auxiliaries, flows, connectors, and/or modules to an existing model in one call. This specific verb+resource+scope distinguishes it from single-item siblings like add_stock, add_flow, add_aux, and add_connector.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies batch use and atomicity ('in one call', 'all-or-nothing'), but it does not explicitly say when to prefer this over the single-add sibling tools or mention any exclusions. Usage guidance is therefore implied rather than stated.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.